Disubstituted cyanoalkanoylureas and thioureas and methods for their production



Patented June 3, 1952 DISUBSTITUTED CYANOALKANOYLUREAS- AND THIOUREAS AND METHODS FOR THEIR PRODUCTION Viktor Papesch, Morton Grove, and Elmer F. Schroeder, Chicago, 111., assignors to G. D. Searle & (30., Chicago, 111., a corporation of Illinois No Drawing. Application April 13, 1950,

Serial No. 155,77 8

2 Claims. 1

The present invention is concerned generally with organic nitriles and more particularly with compounds of the general structural formula,

l RNHn J-NR'00(OH7)..0N wherein n is an integer smaller than 3, X is a chalcogen, R and R. represent members of the group consisting of alkyl, cycloalkyl and aralkyl radicals and wherein one of the radicals R and R contains a minimum of three carbon atoms. In the foregoing structural formula X represents a chalcogen or non-metallic element of group 6 such as oxygen and sulfur. Among the radicals which one of the substituents R and R may represent are normal and branched chain propyl, butyl, amyl, hexyl and octyl radicals, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, benzyl, phenethyl and phenylpropyl radicals, the other substituent being a member of the same group, methyl or ethyl. The R and R. groups may be different or identical.

The nitriles of this invention have been found to possess useful therapeutic properties, particularly as cardiovascular, diuretic and chemotherapeutic agents. Further, they are valuable intermediates for the production of other medicinal agents such as uracils, thiouracils, xanthines and thioxanthines. The uracils and thiouracils formed by cyclization of certain of these nitriles are described in our copending applications, Serial No. 138,074, filed January 11,. 1950, now Patent No. 2,567,651, and Serial No. 141,836, filed February 1, 1950. The present application constitutes a continuation-in-part of these applications.

The prior art discloses several N,N"-dialkyl substituted N-cyanoacetylureas in which the alkyl group represents methyl and ethyl radicals. However, these compounds have not been found therapeutically useful, whereas the nitriles of this invention have shown a high degree of pharmacodynamic effectiveness. Thus in pharmacological trials in rats, using the Lipschitz method of evaluating diuresis, (Journal of Pharmacology and Experimental Therapeutics, '79, 97; 1943) the N-ethyl-N-isopropyl-N-cyanoacetylurea far surpasses such standard diuretics as theophylline and theobromine in effectiveness. Furthermore, such nitriles are much less toxic than these Xanthines and lack such undesirable side effects as the tendency to produce emesis.

The compounds of our invention may be prepared by a number of methods. One of the preferred procedures is to heat the LB-disubstituted urea or thiourea with acetic anhydrlde and cyanoacetic acid or cyanopropionic acid for 30 to 200 minutes at 50-100 C. We have discovered that in the case of unsymmetrically substituted 1,3-dialkyl ureas and thioureas the substitution of the cyanoacyl group occurs primarily at the nitrogen atom to which the smaller alkyl group is attached. Thus, if R is a radical containing more carbon atoms than R, the substitution occurs primarily as follows:

condensed with anisocyanate or isothiocyanate of the type R-N C X.

I Obviously in this case it is immaterial whether or not the R group is larger or smaller than the R group. However, the yields obtained by this method are inferior to those obtained with the method mentioned above.

On evaporation of the solvent used for the condensation under reduced pressure, the cyanoacylureas and thioureas are usually obtained as syrups, but in a few cases they become crystalline readily. The syrups may be further purified by high vacuum distillation. In order to establish their structure, the compounds in which, n was one, i. e., the cyanoacetyl derivatives, were usually converted to the corresponding 6-amino-,-1,2,3,4- tetrahydro-2,4-pyrimidinediones and 2-thio-6- aminoe1,2,3,4-tetrahydro-2,4-pyrimidinediones of the formula. v v

'ing and stirring, solidifies.

This cyclization is eflected by heating with a dilute alkali solution. The position of the groups R and R in the substituted pyrimidinediones was verified by alkylating-or aralkylating in--the 3 position the l-monosubstituted Gamma-1,23,4- tetrahydropyrimidinedione, the latter being derived from the monosubstituted cyanoacetyl urea,

A number of new N ,N-disubstituted .ureas' have: been prepared and are described herein. .We

have found that one of the most economical and direct methods'of preparing suchureas is to add one molecular equivalent of analkyl carbaininoylchloride to one molecular equivalent of an alkylamine in the presence of at least one equivalent of alkali with efiicient cooling. The processmay V be represented schematically as iollows:

RNH-COC1+RNHz+NaOH- rh f ii w ng xainpies illustrate t; detail c ritain-pf the; compounds. which; comprise this ingvention; and methodsof producing them; The

invention-is 1 not to be construed as limited in spirit or in-scQD'? l hereby. it will be. apparent to those skilledjn-the art that manymodifications inmaterials.-;and,- methods may be; made; without departing; 'from our invention. In these examples the temperatures are given indegrees centigrade, the parts by volume in milliliters (ml.), the parts by weight in grams (g.) and pressures during: vacuum distillation in millimeters .(mm:) .01 microns of mercury.

EXAMPLE I N -Imah' i-w;eyanoacetyz-N asopio yzurea A .t1utii;;ci 10g. of methyl isocyanate in 50 mlrof benzene-- is cooled in ice and; treated by the slow additionoi an ice-cold-solution of '15 g.

i-isen qe le fliee in: 5 m bnzehe After completion 'of the addition, the benzene-is re! m y uebyr vacuu distillation: The residual syrup crystallizes on cooling'to give-1's g: of practically pure N-isopropyl-N=methylurea, melting at 92-94? C. On recrystallization froma mixture of parts of ethyl acetate and 10 parts of ethyl ether, long needles melting at 94-96" C. are

C. in awaterbathx The solvent. is removed as completely as possible by vacuum distillation. ml; of water is added to the residue and vacuum distillationcompleted.- The syrup consists of 'N- methyl .N 2 .cyanoacetyl N isopropylurea. Distillation at'20 micronspressure yields a colorle'ss liquid;

at'80? C., a melting point of 210-212 C. is obtained. or r EXAMPLE 2 N -methyZ-N -cyanoacetyl-N -z'sopropylthiowea conducted atsuch a rate that the temperature remains at'20-25" C. Stirring is continued for Zminutes. TheN isopropyl-N'-methyl-thiourea-crystallizes out. One cools, filters, washes with benzeneaiid-finally with petroleum ether. 91 g. of the urea'derivative are obtained in hexagonal plates; melting at 98-l00 C.

26.4 g. of'this urea are dissolved in '75 ml. of acetic anhydride and treated with 20.5 g. of cyanoacetic acid. On heating for 2 hours at 60 C. a very deep red color develops. If, instead, one heatsfor on1y15 minutes at 75. Ova-much lighter color is obtained. The. solvent is removed under vacuum as far as practical. Onethen adds 60 ml. of water and resumes the distillation until 50 g. of athick, red syrup are obtained, consisting of Nfniethyl-N cyanoacetyl-N'-isopropylthiourea. Acolorless liquid is obtained by distillation at 25 microns pressurer To establish the stru'ctuie of this compound, 7

40 g. of this syrup aremixed-with 40 ml. eweter and treated with-6-ml; of 70% sodium-bydroxide.- The alkali is suitably added nun. portions, to prevent heating.- The'syrup dissolves and, almost immediately thereafter, there is" a precipitation of a yellowish solid. After" standingfora half hour-"one dilutes with iiil. o'f water, filters, washes wit h' water andfiriesfl 34 g. oi crude 1 isop py1 ==2:= thio 3 methyl-6 amino- 1,2,3;4 tetrahydro-2,4-pyrimidinedione are thus obtained. Upon recrystallization from glacial acetic acid, colorlessneedle's'iorm; which melt at 247-248" C.

EXAMPLE 3 N-ethyl-N cyahoacetyl-N '-propylurdrd an ice cooled sciatica of tag; ofet-hyl-isoe cyanatein 300 mLof-b'enzene are added,= with stirring, a solutionpf 54.5,g; of n-propylamine 111200 ml. of benzene, the temperature-oi there- 'actio'ri being held-at..about 15-to 2 59 C. After completion of ins am-me thesolvent is re moved by vacuum. distillation-.- The; residual syrup crystallizes oncooling-to give 108 g..;of-'N= propyl-N ethylurea in, practically pure. form. On recrystallization from 10 parts of petroleum ether, needles meltingat 79-'-80- -C. are obtained. This urea derivativemay beobtained'bya more economieal method by;add-i-ng.2l.6 g.,,of anymmamm chloride dropwise -into;;a n--- iceg cooled mixture of 12 g;-ofn-propylamine llj ml. of sodiumhydroxide and about-e0, .g. of crushed ice." The reaction, is very; vigorous and uponits completion the-Npropyle l l=-eth ylfurea v precipitates. It; may be purified by recryse ta-llization' from petroleum, ether;as;. above and needles melting at- 7940? C. are -obtainedi A'jnixture of 97 g. of the.crude Nepropyh-N ethylurea, $76.5 g. of .cyanoacetic. acid and liiil inl. off'acetic ahhydrideis heated'atfwe C. The heat. of reaction, 'at the start may necs'sitateree iixovai of the conta ner-tram thebathiimtil the main reaction ispcmpi eted The solver-mime:

tilled off as completely as possible. N-ethyl-N- cyanoacetyl-N-n-propylurea is obtained ,as a syrup.

To establish the structure of this compound it was ring closed. 100 g. of the syrup are stirred with 150 m1. of water at 20 C. and treated with 25 ml. of a 70% (by weight) aqueous solution of sodium hydroxide. The syrup dissolves completely, but almost immediately, a second, oily product is deposited. The temperature rises to 70-7 C. then drops again. On cooling and stirring, the oil rapidly crystallizes. Filtration, washing 'with water and air drying gives 66 g. of crude product. Two recrystallizations from hot ethyl acetate and air drying yield 47 g. of 1- propyl-3-ethyl-6-amino-l,2,3,4-tetrahydro 2,4- pyrimidinedione monohydrate in the form of diamond-shaped plates, melting at 86-87 C. To obtain the anhydrous product one heats for 24 hours at 80 C. and recrystallizes from parts of ethyl acetate. The fine white needles melt at 166-167 C.

I EXAMPLE 4 N -ethyZ-N -cyanoacetyZ-N '-propylthiourea 30 g. of l-n-propyl-3-ethylthiourea are dissolved in 75 ml. of acetic anhydride and treated with 20 g. of cyanoacetic acid. One heats for 20 minutes at 70-75" C. and vacuum distils to remove the solvent as far as convenient. Then one adds 100 ml. of water and resumes the distillation to obtain the N-ethyl-N-cyanoacetyl- N-propylthiourea. This syrup is cyclized by treatment with slightly more than the necessary amount of 20% sodium hydroxide to make the solution alkaline to phenolphthalein paper. The alkali is added slowly so as to avoid excessive heat development. Crystallization occurs soon thereafter. The yellowish precipitate of l-npropyl-2-thio-3-ethyl-6-amino 1,2,3,4 tetrahydro-2,4-pyrimidinedione is filtered and washed with water and may be obtained in colorless form by recrystallization from dilute ethanol.

EXAMPLE 5 N -ethyZ-N -cyanoacetyl-N -isopropylurea From 79 g. of ethyl isocyanate in 300 ml. of benzene and 82 g. of isopropylamine in 200 ml. of benzene one obtains, by using the procedure of Example 3, 134 g. of N-isopropyl-N'-ethylurea, which, on recrystallization from ethyl acetate, melts at 158-l59 C. 91 g. of the crude product is reacted with 71 g. of cyanoacetic acid and 175 ml. of acetic anhydride as in Example 3 to obtain 160 g. of a syrup, consisting of N-ethyl- N-cyanoacetyl-N'-isopropylurea. I

100 g. of this syrup in 150 ml. of Water are then reacted with 30 ml. of a 70% aqueous solution of sodium hydroxide. Proceeding as in Example 3 one obtains 64 g. of crude 1-isopropyl-3-ethyl-6- amino l,2,3,4-tetrahydro 2,4 pyrimidinedione, which on two recrystallizations from methanol and drying at 80 C. for 12 hours gives 27 g. of cubical prisms melting at 200-201 C. containing no water of crystallization.

EXAMPLE 6 N,N'-di-n-propyl-N-cyanoacetylurea 270 ml. of a cooled 70% sodium hydroxide solution are added to a solution of 300 g. of n-propylamine in 650 ml. of ice water in a 5-liter flask with mechanical stirring. A solution of 263 g. of phosgene in 1320 ml. of benzene, prepared at 20 C. is added to the reaction mixture with cooling at 0-5 0. in the course of two hours. Toward the end of the reaction, the temperature is permitted to rise to about 11 C. Stirring is continued for a half hour. The aqueous layer is separated and washed with benzene, the benzene solutions are united and dried over anhydrous The benzene is then distilled syrup may be purified by high vacuum distillation at 550- C. and at 20-30 microns pressure. The distillate is a colorless liquid. I

To obtain the pyrimidine derivative 550 ml. of

a 10% sodium hydroxide solution are added to this nitrile and the pH adjusted to fairly strong alkalinity to phenolphthalein. The solution becomes hot and an oil is formed which on stirring and cooling crystallizes. The resultant monohydrate of 1,3-di-n-propyl 6 amino 1,23,4- tetrahydro-2,4-pyrimidinedione is recrystallized from 20% ethanol. The white crystals soften at 94 C. andmelt at 98-100? C. By drying at 80 C. for 8 hours anhydrous crystals are obtained which melt at 136-138.5 C.

EXAMPLE 7 N,N'-di-n-propyZ-N-cyanoacetylthiourea 27 g. of 1,3-di-n-propylthiourea are dissolved in 50 ml. of acetic anhydride and 50 ml. of acetic acid. To this solution one adds 17 g. of cyanoacetic acid and heats for 20 minutes at 55 C. Most of the solvent is then removed by vacuum distillation at a bath temperature of 50 C. 25

'ml. of water are'added and the distillation resumed until the syrup of N,N'-di-n-propyl-N- cyanoacetylthiourea is obtained.

This syrup material is cyclized by addition of 20% sodium hydroxide, until the pH reaches 10. One stirs until crystallization occurs, cools, filters and Washes repeatedly with water. In order to obtain colorless crystals of 1,3-di-n-propyl-2- thio 6-amino-l,2,3,4-tetrahydro-2,4-pyrimidinedione one recrystallizes from 20% ethanol.

EXAMPLE 8 N- ethyZ-N-cyanoacetyZ-N' -n-butylurea Proceeding as in Example 3, 108 g. of crude N-ethyl-N-n-butylurea, whichmay be prepared by the method of E. M. Schultz (J. Am. Chem. Soc. 69, 1056, 1947), is reacted with 76.5 g. of cyanoacetic acid and 200 ml. of acetic anhydride to obtain g. of syrup consisting of N-ethyl-N-cyanoacetyl-N-n butylurea. To establish the structure of this compound 50 g. of this syrup are treated with 50 ml. of water and 10 m1. of 70% sodium hydroxide solution, and 44 g. of crude ln-butyl-3-ethyl-6-amino 1,2,3,4-tetrahydro-2,4- pyrimidinedione are obtained. The latter is twice recrystallized by dissolving in 5 parts of ethyl acetate and adding 4 parts of petroleum ether. 24 g. of the monohydrate is thus obtained as a colorless solid oi indefinite crystalline form, melting at 70-7 2 C.

, 7 '-'5.7f"g. dr 'cyaneaeeac acid, heats-for2t 'ininute C ana' v cuum distilsiat a bathtemperature oi fiil v of. the solvent' removed. 1 0' m1. "o'fwat'er are "added and the distillation u'ined iii-mar the N;N -'di-isobiityl-N cyanoacetyl thioiirea forms *a "thick'syrup. 1 v I 4 To -'cyclia'e this material, one adds l-il%"sodiu'm nyameae to Bring the 'pH to T ahdthr'ih furfthe'r small 1 quantity 6f 75% sodium hyd'ro'xiie to raise the "pl-I to about-1'0. The smiiuenpeeomes rather hot and one stirs until-the 'crystall'iza'tion begins. One filters and "washes' repeatedly' with water. The resultant crystals of 1,3-di-isobutyl- 2-thio-6-amino 1,2;3j4 tetrahydro-2A-pyrimidinedione are usuallyyellowish. Toobtain clear crystals one'recrystallizes'from a' lar'ge vtilu'me of dilute ethanol --and uses :charcoal as clarifying age t.

To Y an doe-cooled solution'of 7.1 g. of ethyl :isocyanate inBUO ml. of benzene-1is added,-- with stirring, a solutizinof SOtg. of hexylamine'in 200 :ml.

of benzene. One :coolsto control -reaction and, upon its completion, evaporates the :solvent acetic anhydride, 80 g. 'of glacial acetic acid -and 60g. 1 of -cyanoacetic:-acid are heated'foriz hours at =5-65 C. Vacuum distillation removes most of the solvent. 7 One then adds :150 ml. of water-and resumes the vacuum distillation until all of the solvent has disappeared. The N-ethyl-N-cyanoacetyl-N-hexylurea is thus obtained as a syrup. In order to bring aboutringfclosure enough 10% sodium hydroxide is added to make the solution alkaline tophenolphthalein. "Onewarm'sfltom C. and the temperature is maintained "at "IO-80'? fC. Upon cooling a" waxy material isobtaine'd; which on washing with water -and repeated recrystallization ffr'om ethanol yields 1'=hexyl -3 ethyl 6- amino -"-1','2',-3-,4*- tetrahydro 2;4pyrimidinedicne.

The white crystals melt atI-BO l GB C;

cyar'iate in 400ml? of benzeneiisgraduallyeadded, with stirring,-asolution of :1 88 ggsofwyclohexylaa mine in 300- ml. of benzene, theitemperature'uelng held below C; .-Partial :crystallizati'on ioccufs anti-Finest during the reaction. The mixture is 'ti arisferredl l to a large dishand the solvent evaporated on a steam;bath-Q The -color-less,.-crystal1 ine residue,

consisting of practically pure N-cyclohexyl-N' 'ethylurea weighs 316 g. Recrystallizationirom 10 parts of ethyl acetate gives needles -melting at 113-1 15 o. I v V H A mixture of 316 g. of N-ethyl-N'ecyclohex'ylurea, 19( -g,.cyanoacetic acid and-600 ml. of acetic anhydrideis heated for 3 hours-on a water bath heldlat about C. The solvent is removed as faraspossibleby vacuum distillation, the syrup poured mus beaker, covered with '200 ml. of

water and :stirred. The syrup crystallizes rapid '20 'g. of -l-benzyl-'3 -ethyl-thiourea are disse1ved m 40=mL0f g'lacialacetio-acidand 40 ml. of acetic anhydri'de. D ne then adds 1158 g. of cyanoa'cetio acid, heats for 1-5mi'nutes at -'60 C. and vacuum distils at a bath temperature of BO' C. until' most "of *the solvent is removed. "20' -in1. -of' water are added and "the distillation is resumed. A thick syrup isobta'ined which con- "sis ts of 'N-ethyl N-cyanoacetyI-N-benzylthidu- -rea.

'ln order to efiect-ring closure one addsa 20% aqueous sodium hydrox ideso'lution to raise the pH to about 10.- The solution becomes rather hot and one stirs until aprecipitate begins to form. The yellow crystals of *1-benzyl-'2-thio-3- ethyl 6 amino 1,2-,3,4 tetrahydro 2,4 ipyrimidine'dione are 'filtered and washed repeatedly'with' water. Whitecrystals'may be obtained hytcrys'tallization"from 50% 'ethanol using :charcoal. 7

d N;N--dibenzyl- N-cyanoacetylurea 290g. of dibenzylurea are dissolved in 350 ml. of glacial acetic acid-and-350.ml.,of=aceticanhy- -dride. g. of cyanoaeoticxaeid- 'arewadded and -the mixture keptat (EU-65 C. for 2rhours. The solvent is evaporated 1 in vacuum on the steam bath After removal of about 500- ml.:of=solvent, ,th'e l\ T -,N'-dibenzy1eNecyanoacetylurea begins to crystallize; V

Cyclization may 'be-accomplishedby treatment pliadilute-alcoholic solution with alkali. The "1,3 dibenzyl 6 amino- --1;2,3,4- -tetrahydro 2,4-pyrimidinedione may be crystallized from 50% ethanol, the scolorless crystals melting at about 120-125 C. v p

We-claimz 1; Abompound'ofith'e striiotural formula f-whereinaR ian .zalliyl group iof'z'no zmore than three carbon atoms.

9 10 2. A compound of the structural formula UNITED STATES PATENTS CaH7NHCO-N(C2H5)COCI-I2-CN Number Name Date I! VIKTOR PAPESCH. 2,313,498 Allen et a1 liar. 9, 1943 ELMER F. SCI-IROEDER. 5 FOREIGN PATENTS Number Country Date REFERENCES CITED 175,415 Germany Sept. 14, 1906 The following references are of record in the OTHER REFERENCES file this patent: 10 Beilstein (Handbuch, 4m ed), v01. 4, p. 77 

1. A COMPOUND OF THE STRUCTURAL FORMULA 